第1章例子-一个简单的flex词法分析器
一个简单的flex词法分析器
代码(001_3_simple_flex_app.l)
/* 识别出用于计算器的记号并把他们输出 */%%
"+" { printf("PLUS\n"); }
"-" { printf("MINUS\n"); }
"*" { printf("TIMES\n"); }
"/" { printf("DIVIDE\n"); }
"|" { printf("ABS\n"); }
[0-9]+ { printf("NUMBER %s\n", yytext); }
\n { printf("NEWLINE\n"); }
[ \t] { }
. { printf("Mystery character %s\n", yytext); }
%%
Makefile(model.Makefile)
FILE_NAME = $(file_name)FLEX_INPUT_FILE = $(FILE_NAME).l
FLEX_OUTPUT_FILE = $(FILE_NAME).c
FLEX_CMD = flex
FLEX_FLAG = -oGCC_CMD = gcc
GCC_COMPILE_FLAG = -c
GCC_OUTPUT_FLAG = -o
GCC_LINK_FLAG = -lfl
GCC_OBJECT_FILE = $(FILE_NAME).oTARGET_FILE = $(FILE_NAME)all: clean flex_main gcc_mainflex_main: $(FLEX_INPUT_FILE)$(FLEX_CMD) $(FLEX_FLAG) $(FLEX_OUTPUT_FILE) $(FLEX_INPUT_FILE)gcc_main: $(FLEX_OUTPUT_FILE)$(GCC_CMD) $(GCC_COMPILE_FLAG) $(FLEX_OUTPUT_FILE) $(GCC_OUTPUT_FLAG) $(GCC_OBJECT_FILE)$(GCC_CMD) $(GCC_OBJECT_FILE) $(GCC_LINK_FLAG) $(GCC_OUTPUT_FLAG) $(TARGET_FILE).PHONY: cleanclean:@rm -f $(FLEX_OUTPUT_FILE)@rm -f $(GCC_OBJECT_FILE)@rm -f $(TARGET_FILE)
编译指令
make -f model.Makefile file_name=001_3_simple_flex_app
测试指令
./001_3_simple_flex_app
#输入以下信息，按Ctrl+D结束
12+43
5 6 / 7q
输出信息
